non-protein nitrogenous compounds

non-protein nitrogenous compounds

nitrogen-containing substances not classified as proteins

protein and nucleic acid catabolism

non-protein nitrogenous compounds result mainly from

renal and hepatic function, metabolic disorders, nitrogen balance

NPN compounds help assess

Formed in the liver from amino groups and free ammonia during protein catabolism; filtered by the glomeruli; most is excreted in urine, some reabsorbed in renal tubules.

How is urea formed and eliminated in the body?

prerenal azotemia

caused by decreased blood flow to kidneys, e.g: shock, dehydration

renal azotemia

caused by intrinsic renal damage, e.g. glomerulonephritis

postrenal azotemia

caused by obstruction (e.g. stones tumors)

10:1

what is the normal BUN/Creatinine ratio

prerenal azotemia

increased BUN/Creatinine ratio

renal azotemia

decreased BUN/Creatinine ratio

postrenal azotemia

increased or normal BUN/Creatinine ratio

purine catabolism

uric acid is the end product of —- primarily in the liver

gout, renal calculi, purine metabolism disorders

uric acid helps diagnose and monitor

tophi

deposits of monosodium urate crystals in soft tissues, typically seen in chronic gout

6.8 mg/dL

plasmic uric acid solubility threshold

lesch-nyhan syndrome

An X-linked disorder caused by HGPRT deficiency, leading to excess uric acid.

self-mutilation, neurological deficits, hyperuricemia

lesch-nyhan syndrome is characterized by

uricase, peroxidase-coupled

enzymatic method for uric acid determination

isotope dilution mass spectrometry (IDMS)

the reference method for uric acid determination

creatine

phosphorylated in muscle to creatine phosphate

creatine phosphate

converts to creatinine non-enzymatically

urine

where is creatinine excreted?

plasma creatinine

It reflects muscle mass and kidney function

inversely related

relationship between plasma creatinine and glomerular filtration rate

Jaffe reaction

A colorimetric assay for creatinine using picric acid in alkaline medium.

nonspecific, interfered by glucose, ketones, and other substances

limitation of jaffe reaction

Risk, Injury, Failure, Loss, ESRD

What are the criteria and stages in the RIFLE classification of Acute Kidney Injury (AKI)?

ammonia

In liver failure, what accumulates in blood?Ammonia accumulates in the blood due to the liver's inability to convert it into urea for excretion.

free ammonia

neurotoxic, the liver converts it to urea via the urea cycle

severe liver dysfunction, urea cycle disorders, Reye’s syndrome

Elevated plasma ammonia indicates

arterial ammonia

more reliable than venous ammonia

GLDH method in ammonia analysis

It uses glutamate dehydrogenase to catalyze a reaction consuming NADPH, measured by a decrease in absorbance at 340 nm.